1. Field of the Invention
The present invention relates to a signal processing apparatus and a signal processing method configured to upconvert stored content data.
2. Description of the Related Art
Currently, the maximum number of effective pixels specified in the high definition (HD) standards employed in Japanese digital broadcasting is 1920×1080. Furthermore, for example, Nihon Hoso Kyokai (NHK) has conducted research about a technique related to high definition content called a super high definition (SHD) and ultra-high definition (UHD) that realizes an image of a larger number of pixels.
That is, the maximum number of effective pixels of the SHD (or UHD) is 7680×4320 (8 k×4 k), which is far beyond the HD standard. Further, a digital cinema having a 4096×2160 (4 k×2 k) video format has been developed. Regarding a sound quality, research has been underway to develop a 22.2 multi-channel system which realizes three-dimensional sounds of a quality higher than sounds generated with current 5.1-channel surround-sound techniques.
In recent years, research has been conducted into techniques for enhancing (upconverting) a quality of video images of a conventional standard definition (SD) format and for enhancing a quality (upconverting) of low-quality sounds. In addition, various techniques relating to upconversion processing have been developed for realizing more realistic and powerful video images and sounds using intricate algorithms.
For example, a technique for upconverting an SD image to an HD image by classification adaptive processing is discussed (see Japanese Patent Application Laid-Open No. 07-321662). Further, a technique for improving a sound quality that converts a format of audio data to reproduce delicate sounds or nuance is discussed (see Japanese Patent Application Laid-Open No. 09-261071).
Upconverting methods are roughly classified into a real-time processing method that processes content data while reproducing the data and a method for processing content data over time instead of processing in real time. In a case of performing processing with a relatively low load such as image or sound quality correction currently executed in general digital television receivers, image or audio data is processed in real time while broadcast signals are received.
However, in the future, it is anticipated that a digital television receiver or other peripheral devices will be equipped with a function for executing upconversion processing (image/sound quality raising processing) that is difficult to execute in real time because of its high processing load. Since the upconversion processing with a high processing load is difficult to perform in real time, content data is temporarily stored in a recording medium and then, the stored content data is gradually upconverted.
In such a case, if the upconversion processing is time consuming, the upconversion processing may not be completed by the time a user desires to reproduce the content data. In particular, in the case where a plurality of content data are to be upconverted in turn, if a content which a user desires to reproduce is placed at a later point in the content data, the desired content may not be upconverted immediately. Accordingly, it is desirable that user's preferences are reflected so that the desired content is preferentially upconverted.
For example, Japanese Patent Application Laid-Open No. 2006-086639 discusses a technique related to user's preferences which deletes contents from a storage unit or compress them in an ascending order of user's preference level to save a capacity of a recording medium.
As described above, if the upconversion processing is time consuming, there arises a problem that content data cannot be reproduced at a timing a user wants because the upconversion is not yet finished. In particular, in the case of upconverting a plurality of content data, a content that a user wants to reproduce may not be immediately upconverted.